The present invention relates generally to circuit substrates and, more particularly, to a circuit substrate manufactured using metal powder and three-dimensional printing.
Typical types of packaged semiconductors are Quad Flat Package (QFP) semiconductors that are formed with a semiconductor die mounted to a lead frame. The lead frame is formed from a sheet of metal that includes a die attach pad often called a flag, tie bars that attach the flag to a frame, and lead fingers. The lead fingers are electrically connected to bonding pads of a semiconductor die with bond wires. The lead fingers provide a means of easily electrically connecting the die to circuit boards and the like. After wire bonding, the die, bond wires, and portions of the lead fingers are encapsulated in a plastic material leaving only sections of the leads fingers exposed. These exposed leads are cut from the frame of the lead frame (singulated) and bent for ease of connection to a circuit board. However, the inherent structure of QFP packages results in limiting the number of leads, and therefore the number of package external electrical connections, that can be used for a specific QFP package size. Further, the external electrical connections of the lead frame based grid array packages are typically fabricated from a thin single sheet of conductive material, such as copper or aluminium, and these connections may not be sufficiently held within the encapsulating compound (material) and may become lose.
An alternative to lead frames in the assembly of semiconductor devices, is the use of circuit substrates. These substrates have internal and external mounting pads interconnected typically by vias and runners such that the substrates resemble miniature Printed Circuit Boards (PCBs). The assembly of a semiconductor device with such substrates typically includes directly mounting of the die bond pads to the internal mounting pads of the substrate and then encapsulating the die with a molding compound. The external mounting pads of the substrate provide external connections as a grid array that are typically mounted to a larger circuit substrate such as a PCB or similar structure.
Current processes for the manufacture of the above circuit substrates are relatively complex and expensive. These processes include the use of masking, etching, plating and cleaning, which can be time consuming and may use environmentally unfriendly chemicals. Accordingly, it would be advantageous to have a simpler and less expensive method of making a circuit substrate.